Difference between revisions of "Using SinCos encoder"

Revision as of 23:14, 21 June 2017

SinCos encoder is an position feedback device similar to quadrature encoder, except instead of outputting digital square waves/pulses, it outputs analog voltages with sinusoidal shape. This signal may be interpolated to yield higher resolution than the equivalent digital signal. Various Granite Devices drives support SinCos encoder feedback out of the box without additional converters or modules.

Configuration

Wiring

Follow your drive's encoder wiring guidelines to connect an SinCos encoder. I.e. for IONICUBE and SimuCUBE products, see encoder wiring table at IONI & IONICUBE user guide/Wiring_overview. For other products, find their equivalent documentation from this wiki.

Relevant parameters

To use SinCos encoder with analog sine and cosine voltage outputs, select the SinCos encoder from Granity's feedback device list Feedback deviceFBD. The interpolation factor determines how many times the resolution is increased from the base resolution. Choices are:

• 16X = equals resolution of encoder which has 16 times higher line count than non-interpolated encoder. I.e. 1000 lines encoder would yield 1000*4*16=64000 couns/rev resolution.
• 64X = equals resolution of encoder which has 64 times higher line count than non-interpolated encoder. I.e. 1000 lines encoder would yield 1000*4*64=256000 couns/rev resolution.
• 256X = equals resolution of encoder which has 256 times higher line count than non-interpolated encoder. I.e. 1000 lines encoder would yield 1000*4*256=1024000 couns/rev resolution.

In addition to choosing interpolation factor, the feedback device resolution parameter Feedback device resolutionFBR need to be set accordingly: multiply the base resolution with interpolation factor. I.e. with 1000 line encoder and 16X interpolation, set FBR to 16000.

As resolution of feedback device changes, the motor travel per one "step" also changes. This affects the velocity and acceleration speed settings. Always check and update other parameters after interpolation factor is changed.

With very high resolution feedback devices, one may run into a problem of limited value range of velocity and acceleration parameters (i.e. velocity limit is set to maximum, but higher value would be desired). To overcome this, reduce Setpoint dividerDIV parameter value which sets the scale of velocity/acceleration limits. I.e. if you change DIV from 100 to 10, you will get 10 times more range in velocity limit. Also change Setpoint multiplierMUL accordingly if the original scaling of setpoint is desired.

Setting parameters

1. Choose Feedback deviceFBD SinCos encoder with desired interpolation factor
2. Update feedback device resolution Feedback device resolutionFBR to match the new setting (see details in above)
3. Check and update velocity/acceleration limits if needed